The present disclosure relates generally to electrical machinery such as motors and generators and, more particularly, to an electrical machine apparatus having high torque density magnetic gearing integrated therein.
Electrical machines (e.g., motors, generators) typically deliver more power at high speeds than at low speeds. In order to adapt a high-speed, rotating electrical machine to a high-torque, lower speed mechanical component (e.g., a prime mover in the case of a generator and a load in the case of a motor), mechanical gear boxes are extensively used as the cost of having a high-speed electrical machine coupled with corresponding mechanical gearing for speed/torque conversion is lower than that for a low-speed electrical machine. As is well known, certain disadvantages are inherent with mechanical gearing such as, for example, acoustic noise, vibration, reliability and the need for lubrication and maintenance, to name a few.
The concept of magnetic gears has also long been in existence, and can potentially offer significant benefits with respect to their mechanical counterparts, primarily as a result of the lack of physical contact between an input shaft and an output shaft. For the most part, magnetic gears have traditionally received relatively little attention in the industry due to the complexity of the proposed designs, as well as the limited torque density such gears can provide. For instance, a magnetic gear assembly arranged in a spur configuration results in only a small fraction of the permanent magnets located on the gears actually contributing to torque conversion at any given time.
More recently, however, a planetary-like magnetic gear arrangement using rare-earth permanent magnets has been proposed, which results in a favorable torque transmission density capability between an outer rotor and an inner rotor. In such a configuration, each of the permanent magnets affixed to the outer rotor and the inner rotor contribute to torque transmission. In view of the existence of a magnetic gearing capability providing comparable transmitted torque density with respect to conventional mechanical gearbox arrangements, it is therefore desirable to be able to provide more functionally integrated electromechanical energy conversion systems that take advantage of this type of non-contact gearing arrangement.